# SI and metric prefix converter

> Convert between SI metric prefixes such as giga, mega, kilo, milli, micro and nano, from quecto (10⁻³⁰) to quetta (10³⁰), including the 2022 additions.

交互版本：https://www.calcopenly.com/zh/conversion/si-prefix-converter
主题：单位换算器

An SI prefix multiplies a unit by a power of ten: kilo is 10³, mega 10⁶, milli 10⁻³ and nano 10⁻⁹. Converting between two prefixes multiplies the value by 10 raised to the difference of their exponents, which moves the decimal point without changing any digits. The converter covers all 24 SI prefixes, from quecto (10⁻³⁰) to quetta (10³⁰).

Engineers and students use it to move between scales of one unit. The default turns the 2.4 GHz Wi-Fi band into 2,400 MHz, a shift of three powers of ten. The unit symbol field only labels the result, so the same conversion works for metres, grams, hertz or watts.

Two BIPM rules apply to every prefix: prefixes are never combined (write nm, not mµm), and because the kilogram already carries one, prefixes attach to the gram: 1 mg, not 1 µkg.

## 输入

- **数值**
- **从** (选项：quetta (Q, 10³⁰), ronna (R, 10²⁷), yotta (Y, 10²⁴), zetta (Z, 10²¹), exa (E, 10¹⁸), peta (P, 10¹⁵), tera (T, 10¹²), giga (G, 10⁹), mega (M, 10⁶), kilo (k, 10³), hecto (h, 10²), deca (da, 10¹), none (10⁰), deci (d, 10⁻¹), centi (c, 10⁻²), milli (m, 10⁻³), micro (µ, 10⁻⁶), nano (n, 10⁻⁹), pico (p, 10⁻¹²), femto (f, 10⁻¹⁵), atto (a, 10⁻¹⁸), zepto (z, 10⁻²¹), yocto (y, 10⁻²⁴), ronto (r, 10⁻²⁷), quecto (q, 10⁻³⁰))
- **到** (选项：quetta (Q, 10³⁰), ronna (R, 10²⁷), yotta (Y, 10²⁴), zetta (Z, 10²¹), exa (E, 10¹⁸), peta (P, 10¹⁵), tera (T, 10¹²), giga (G, 10⁹), mega (M, 10⁶), kilo (k, 10³), hecto (h, 10²), deca (da, 10¹), none (10⁰), deci (d, 10⁻¹), centi (c, 10⁻²), milli (m, 10⁻³), micro (µ, 10⁻⁶), nano (n, 10⁻⁹), pico (p, 10⁻¹²), femto (f, 10⁻¹⁵), atto (a, 10⁻¹⁸), zepto (z, 10⁻²¹), yocto (y, 10⁻²⁴), ronto (r, 10⁻²⁷), quecto (q, 10⁻³⁰))
- **Unit symbol**: Only used for labels, e.g. m, g, Hz, W

## 结果

- 转换后的数值 — 主要结果
- 换算
- Shift in powers of ten

## 公式

$$
x_{\text{to}} = x_{\text{from}} \times 10^{\,e_{\text{from}} - e_{\text{to}}}
$$

## 计算示例

### 2.4 GHz in MHz

- 数值: 2.4
- 从: giga (G, 10⁹)
- 到: mega (M, 10⁶)
- Unit symbol: Hz
- **转换后的数值: 2,400 MHz**
- **换算: 2.4 GHz = 2,400 MHz**
- **Shift in powers of ten: 3**
- 核验来源：giga = 10⁹, mega = 10⁶ (SI Brochure Table 7): 2.4 × 10³

### 1 km in m

- 数值: 1
- 从: kilo (k, 10³)
- 到: none (10⁰)
- Unit symbol: m
- **转换后的数值: 1,000 m**
- 核验来源：kilo = 10³

### 1 quetta in yotta (2022 prefix)

- 数值: 1
- 从: quetta (Q, 10³⁰)
- 到: yotta (Y, 10²⁴)
- Unit symbol: g
- **转换后的数值: 1,000,000 Yg**
- **Shift in powers of ten: 6**
- 核验来源：quetta = 10³⁰ (CGPM 2022), yotta = 10²⁴

### Smallest to largest: quecto to quetta

- 数值: 1
- 从: quecto (q, 10⁻³⁰)
- 到: quetta (Q, 10³⁰)
- Unit symbol: g
- **Shift in powers of ten: -60**
- **转换后的数值: 1 × 10⁻⁶⁰ Qg**
- 核验来源：10⁻³⁰ / 10³⁰ = 10⁻⁶⁰

### 5 µs in ns

- 数值: 5
- 从: micro (µ, 10⁻⁶)
- 到: nano (n, 10⁻⁹)
- Unit symbol: s
- **转换后的数值: 5,000 ns**
- 核验来源：micro = 10⁻⁶, nano = 10⁻⁹: 5 × 10³

## 常见问题

### What are the SI prefixes in order?

There are 24. From largest: quetta (Q, 10³⁰), ronna (R, 10²⁷), yotta (Y, 10²⁴), zetta (Z), exa (E), peta (P), tera (T), giga (G), mega (M), kilo (k, 10³), hecto (h, 10²) and deca (da, 10¹). Then the submultiples: deci (d), centi (c), milli (m, 10⁻³), micro (µ), nano (n), pico (p), femto (f), atto (a), zepto (z), yocto (y), ronto (r) and quecto (q, 10⁻³⁰).

### What are the newest SI prefixes?

Ronna (R, 10²⁷), quetta (Q, 10³⁰), ronto (r, 10⁻²⁷) and quecto (q, 10⁻³⁰), adopted by the 27th General Conference on Weights and Measures (CGPM) in November 2022. They were the first additions since zetta, yotta, zepto and yocto in 1991. On the new scale the Earth's mass, about 5.97 × 10²⁴ kg, is roughly 6 ronnagrams.

### How do I convert between metric prefixes?

Subtract the exponents and move the decimal point that many places. From giga (10⁹) to mega (10⁶) is 9 − 6 = 3 places to the right, so 2.4 GHz = 2,400 MHz; from micro (10⁻⁶) to nano (10⁻⁹) is also 3 places, so 5 µs = 5,000 ns. Moving to a larger prefix shifts the point left: 1,500 m = 1.5 km.

### Why is kilo a lowercase k but mega an uppercase M?

The SI writes the symbols for multiples from mega (M, 10⁶) upward in capitals, while kilo (k), hecto (h), deca (da) and every submultiple are lowercase. The case changes the value: 1 MW (megawatt) is 10⁹ times 1 mW (milliwatt). Writing K for kilo is wrong in the SI, because K is the symbol for the kelvin.

### Does kilo mean 1,000 or 1,024 in computing?

In the SI, kilo always means exactly 1,000, so 1 kbit = 1,000 bits and 1 GB = 10⁹ bytes (NIST). For powers of two the IEC approved binary prefixes in December 1998: 1 KiB (kibibyte) = 1,024 bytes and 1 GiB = 2³⁰ = 1,073,741,824 bytes. The gap grows with size, which is why a 1 TB drive shows about 931 GiB.

### “SI and metric prefix converter”有多准确？

准确性取决于输入值和方法的假设。十进制运算使用50位有效数字，但估算、数值方法和源数据的精度可能较低；显示时的舍入并不能消除这些限制。 已按独立来源核验的计算示例：5。 例如，“2.4 GHz in MHz”根据giga = 10⁹, mega = 10⁶ (SI Brochure Table 7): 2.4 × 10³进行核验。

### 这种方法出自哪里？

BIPM — The International System of Units (SI Brochure, 9th ed.), Table 7: SI prefixes; BIPM — CGPM 2022 Resolution 3: ronna, quetta, ronto, quecto.

## 来源

- [BIPM — The International System of Units (SI Brochure, 9th ed.), Table 7: SI prefixes](https://www.bipm.org/en/publications/si-brochure)
- [BIPM — CGPM 2022 Resolution 3: ronna, quetta, ronto, quecto](https://www.bipm.org/en/cgpm-2022/resolution-3)